I have to ask: where's the option to show trajectories, arcs? I've never actually been able to find anything like it in Blender - so I believe it isn't there (?!). Tell me please.

I know about the "show keyframes" for objects but we really need the arcs for character animation, they're just... well... VERY useful. Why not for objects as well, "just" something that draws a curve between the keyframes. This way one can spot any irregularities in animated movement.

Maybe not on the top of your lists but I hope this could be implemented soon